Determining post core retention/compression strength with metal/non-metal posts

Core post retention is dependent upon post material properties and surface irregularities. Objectives: to compare the retentive and compressive strengths of metal and non-metal post core assemblies. Methods: forty glass fibre (FibreKor, Jeneric/Pentron, Inc.) prefabricated serrated posts, 1.25 mm diameter, and forty serrated stainless steel Paraposts No. 5 (Coltene Whaledent, Inc.), 1.25 mm diameter without insertion tabs, were joined to Build-It Fr (Jeneric/Pentron) dual cure core material in special molds measuring 5Hx5W mm with the post cenetered and with its top surface flush with the core material in the post core complex. For retention, forty samples were separated into four groups of ten samples each according to treatment: 1. No bonding vs. 2. Bonding of FibreKor with silane and Bond-1 primer/adhesive (Jeneric/Pentron), 3. No bonding vs. 4. Bonding of Parapost with Bond-1. For compression, forty samples were separated into four groups of ten samples each as follows: A. no post, B. stainless steel post, C. fiber post and D. centered cylindrical post hole, 1.25 mm diameter. Samples were allowed to set for 96 hours before testing. Tensile and compressive failure loads were measured in a special apparatus in the absence of crowns using an Instron test machine 4505 (Instron) at a cross head speed of 2.5 mm/min. Values were recorded in pounds. For retention, mean values were analyzed with a two-way ANOVA; for compression, a one-way ANOVA was used. Results: In retention, bonding was not significant. Metal posts were significantly more retentive. In compression, the core material was significantly weakened by the metal post. Inclusion of the fibre post did not weaken the post core complex. Conclusions: Metal and fibre posts are different.